Compression pump system

ABSTRACT

According to one embodiment, an apparatus is disclosed that includes a compressor pump and a duty cycle controller. The duty cycle controller controls amount of time that the compressor pump is on each duty cycle. The amount of time is selected so that the compressor pump will operate at a pressure above a desired fill pressure. The operational pressure will generate a restrictive pressure having limited effect on accuracy of pressure reading. Other embodiments are disclosed herein.

PRIORITY

This application claims the priority under 35 USC §119 of Provisional Application 60/617,175 entitled “Compression Pump System” filed on Oct. 8, 2004 and having Mark Higgins and Preyas Shah as the inventors. Application 60/617,175 is herein incorporated by reference in its entirety but is not prior art.

BACKGROUND

Compression therapy is a recognized method for use in treatments with a goal to reduce extremity swelling or increase blood circulation. This therapy may be used to treat patients with indications of lymphedema (tissue swelling), venous disease, a potential for blood clotting, or a need for extra tissue oxygenation to stimulate healing.

Lymphedema is an abnormal accumulation of protein-rich fluid in body tissues. This is caused by an impairment of the lymphatic system resulting in decreased ability to remove fluid from the tissues. This induces swelling and can also lead to skin changes, infection, and decreased wound healing. Lymphatic system impairment can be a congenital condition or result from damage by radiation, surgery, trauma, or infection. Those with lymphedema carry an increased risk of infection because protein-rich fluid accumulation creates an environment favorable to bacterial growth. In addition, there may be associated physical effects including tightness, pain, loss of dexterity, and hardening of the effected tissue.

There are various methods currently employed to treat lymphedema that include medical and physical therapies. Available physical methods may include elevation or compression of the effected extremity with the goal of reducing fluid accumulation. Continuous sustained physical pressure (compression therapy) on an effected limb for a certain amount of time (e.g., approximately 30 minutes) has shown beneficial results to reduce swelling. Compression therapy is usually performed using compression bandages or sleeves. The bandages are typically tight wraps where the sleeves or garments are fitted to the extremity. The sleeve appliance can be elastic, include a series of adjustable straps, or use pneumatically filled chambers to provide pressure to the limb. Air pressure is applied to the various sleeve chambers in pneumatic systems, which in turn, apply pressure to the extremity.

Compression pumps may be used to fill the sleeve chambers. One type of pump and sleeve is intended to apply a uniform pressure over the extremity. However, in order to replicate the lymphatic system it is desirable to have a pump and sleeve system that contains multiple chamber segments that are sequentially pressurized along the extremity, distally to proximally, thereby moving the accumulated fluid from the affected extremities back into the body where it can be naturally eliminated. Compression pump systems can inflate a single or multi chamber sleeve or sleeves (e.g., lymphedema pump sleeve) to apply gentle pressure to an extremity to force fluid back toward the body.

Compression pump systems have resistance to air flow between the pump and the sleeve chamber caused by lengths of tubing, small valve orifice diameters, and inertia of a deflated sleeve chamber. The valves used in lymphedema compression pump systems are typically rotary motor drive type that have a fixed cycle time for each fill and deflate cycle. Alternatively, the system may use a manifold with solenoid valves that can be opened and closed by system electronics at any given time or designated pressure. In both cases, these valves typically have small orifices and cause some flow restrictions. These conditions create resistive backpressure buildup between a pump and regulating valve (or valve manifold).

Typically a pressure sensor is placed at the values to feedback local pressure data to aid in pressure control. An airflow restriction of any kind between a pump and pressure sensor will cause the sensor to read a higher pressure than is behind it in the filling sleeve chamber. The pressure applied to the extremity in compression pump systems is very low, usually lower than 120 mmHg or 2 PSI. It is difficult to both rapidly reach and accurately maintain the low pressures required. Current methods used to achieve accurate pressure readings at the sleeve chamber can take 30 seconds or more to fill.

One method currently employed to increase low-pressure accuracy is to use a low flow pump. This method uses a pump with a low flow rate to minimize the absolute backpressure created by restrictions in the system. Another method uses bleeder valve(s) at the sensor location. A bleeder valve is required at the entrance of every valve inlet port and is individually calibrated to the required chamber pressures to limit the air pressure applied at that point. This method is inherently inefficient because there is always air being bled off during the fill-cycle that cannot be used to fill the sleeve chamber. An additional method uses a variable pump speed to slowly increase the pressure and airflow rate to the chamber being filled. Another technique is to start the pump with a limited power and gradually increase the power used. This technique may utilize a variable resistance to vary (e.g., increase) the applied RMS voltage. All of these methods require the pump to be on all of the time and have a slow fill rate.

A compressor pump with higher pressure and airflow characteristics can be used to shorten the duration to fill a chamber to a desired pressure. However, higher throughput pumps can create a large pressure difference between the manifold and the sleeve chamber thereby limiting accuracy at the low-pressure settings.

What is needed is a compression pump system that can reduce the time to fill the pressure chambers while also providing an accurate pressure reading.

SUMMARY

A compressor pump system is disclosed that can output a pressure and flow rate that will allow a chamber to be filled to a desired pressure in a fast and efficient manner. The compressor pump generates an output pressure that begins above a desired fill pressure and takes into account inherent restrictive backpressure in the system so as to provide an accurate measurement. A pump control device generates the output pressure by adjusting the time that the compressor pump is actually on. That is, for each timed duty cycle the pump may be non-operational for a portion of the time. The duty cycle time frame may be associated to a half alternating current (AC) power wave. An opto-isolator may be used to detect the start of each half wave by detecting a 0 volts (V) AC crossover point. A processor may be signaled of the start of the duty cycle and delay applying power to the compressor pump for a period of time after the detection start of the duty cycle. The longer that the application of power is delayed the less pressure that the pump will provide.

The compressor pump may be utilized to sequentially fill individual chambers of a compression sleeve to different pressures. When the pressure within a sleeve reaches the desired pressure, the next chamber may begin to be filled.

The compressor pump system may include a user interface to permit the user to set fill parameters.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the various embodiments will become apparent from the following detailed description in which:

FIG. 1 illustrates an example compression pump system, according to one embodiment;

FIG. 2 illustrates several examples of restrictions (backpressure) in a pump system affecting the pressure readings, according to one embodiment; and

FIG. 3 illustrates an example functional diagram of a duty cycle control system utilized in a compression pump system, according to one embodiment.

DETAILED DESCRIPTION

FIG. 1 illustrates an example compression system 100. The system 100 includes a compression pump 110, a manifold 120 having a plurality of valves 130, a pressure sensor 140, a compression sleeve 150 having a plurality of chambers 160, and a vent valve 170. The compressor pump 110 outputs air at a desired pressure and flow rate. The compressor pump 110 supplies pressurized air to the manifold 120 via some connection medium (e.g., tubing). The manifold 120 utilizes the plurality of valves 130 to control which chamber 160 to provide the pressurized air. Each of the valves 130 is connected to a corresponding chamber 160 via some medium (e.g., tubing). The pressure sensor 140 measures the pressure associated with each chamber at the manifold 120. The valves 130 may be solenoid valves that can be turned on and off based on signals received (e.g., electronic signals).

A processor may monitor the output from the pressure sensor 140 in relation to desired fill pressure values for the chambers 160 and control when the valves 130 should be turned on and off. For example, once the pressure sensor 140 determines that the appropriate pressure has been reached in one chamber 160, the corresponding valve 130 may be closed and the next valve 130 may be opened. Once all of the chambers 160 have been filled, the processor may signal all or a subset of the valves 130 to open and the vent valve 170 to operate so that chambers can be deflated. The vent valve 170 is used to expel the pressurized air out of the chambers 160 in the compression sleeve 150.

Resistive backpressure exists within the compression system 100. The resistive backpressure is caused by resistance to airflow between the pump 110 and the chambers 160. Contributors to airflow resistance include the lengths of tubing, small valve orifice diameters, and inertia in a deflated sleeve chamber 160. The resistive backpressure will likely result in a pressure reading at the manifold 120 that does not equal the pressure within the sleeve 150. For example, when the pump 110 begins to fill the chamber 160 the pressure sensor 140 is likely to sense a pressure equal to the resistive backpressure while there may be no (or little) pressure in the chamber 160.

FIG. 2 illustrates several examples of restrictions (backpressure) in a compression pump system. The pump system includes a pump 200, a gauge 210 to measure pressure (e.g., at a manifold) and downstream restrictions (e.g., restrictions between the valve and the sleeve). The output pressure of the pump 200 in each of the examples is 100 mmHg, with the airflow directed towards the gauge 210 and downstream plumbing, such as chamber of a compression sleeve (not illustrated).

In the top example, there are no downstream blockages or restrictions and the entire pump output is passed through so that there is no resistive (restrictive) backpressure, and the gauge 210 may initially read 0 mmHg. The pressure built up within the chamber will resist the pumped pressurized air as the chamber fills. The gauge 210 will measure the air that is restricted by the chamber. Accordingly, the gauge 210 will reflect the pressure within the chamber. It should be noted that zero restrictive backpressure is unlikely as there will be some backpressure in the system caused by at least some subset of the length or diameter of the tubing or the diameter of the valve. In the middle example, there is a total restriction (blockage) so that none of the pressurized air passes through the system. Accordingly, the restrictive backpressure is the output of the pump 200 and the gauge 210 would read 100 mmHg. It should be noted that the pump system would not be operational if there was a complete blockage because the sleeve would not be able to get filed.

In the lower example, there is a partial restriction (e.g., 50% blockage) so that some (e.g., half) of the pressurized air from the pump 200 passes through to the chamber and some (e.g., half) of the pressurized air is restricted and is thus measured by the gauge 210 (e.g., 50 mmHg). For a 50% blockage, the backpressure may be 50% of the flow or a backpressure of 50 mmHg. The gauge 210 may read this pressure soon after the pump 200 begins to operate. If the sleeve is set to be filled to a pressure lower then the backpressure (e.g., 40 mmHg), the initial gauge reading (e.g., 50 mmHg) may cause the pump 200 to either shut off or switch to the next chamber before the current chamber reaches its desired pressure.

The examples in FIG. 2 indicate that the more restriction there is to the flow of air, the higher the reading will be at the gauge 210. While the examples appear to indicate that the pressure reading is linear with the amount of restriction (e.g., 0%=0 mmHg, 50%=50 mmHg) it is clearly not limited thereto. Rather, the relationship may be exponential where as the pressure applied is reduced the backpressure increases as a percentage. For example, if 100 mmHg is applied the backpressure reading at the gauge 210 may read 20 mmHg (20%), where if 50 mmHg is applied the backpressure reading at the gauge 210 may read 15 mmHg (30%).

The examples of FIG. 2 focused on the initial readings at the gauge 210 when the pump 200 initially starts to operate. As the sleeve begins to fill the pressure recoded at the gauge 210 will continue to increase as the pressure in the sleeve increases (the pressure in the sleeve acts as a backpressure). However, the pressure recoded at the gauge 210 may not linearly increase with the pressure within the sleeve. Rather, as the pressure in the sleeve increases a portion of the increase may be recorded on the gauge 210. That is, the amount of restrictive backpressure in the system may be reduced.

For example, if 60 mmHg is being pumped an initial gauge reading of 12 mmHg would indicate that there is 12 mmHg of restrictive backpressure. When the sleeve has 10 mmHg, the gauge 210 may read 21 mmHg indicating that the restrictive backpressure is 11 mmHg. When the sleeve has 20 mmHg the gauge 210 may read 29 mmHg indicating that the restrictive backpressure is 9 mmHg. When the sleeve has 30 mmHg, the gauge 210 may read 36 mmHg indicating that the restrictive backpressure is 6 mmHg. When the sleeve has 40 mmHg the gauge 210 may read 42 mmHg indicating that the restrictive backpressure is 2 mmHg. At some point the measured pressure and the pressure within the sleeve will equalize (the amount of pressure increase in the sleeve will equal the amount of increase measured at the gauge 210). For example, when the sleeve has 50 mmHg the gauge 210 may read 52 mmHg indicating that the restrictive backpressure is still 2 mmHg and thus indicating that the gauge pressure and the sleeve pressure are in equilibrium. The pressure recorded at the gauge 210 may always be higher than the pressure within the sleeve due to residual backpressure.

In the above example, if the desired fill pressure of the sleeve was 30 mmHg the pump 200 would turn off or switch to the next sleeve when the desired fill pressure was 30 mmHg or less (gauge reads 36 mmHg when sleeve is at only 30 mmHg). That is an error rate of approximately 20 percent. Such an error rate is likely unacceptable. Accordingly, in this example the pressure setting of the pump 200 was set to high because the initial resistive backpressure was not reduced an acceptable amount buy the time the desired fill pressure was measured. Selecting a pump pressure for a desired fill pressure that is too high may result in an inaccurate pressure measurement.

One way to avoid the inaccurate pressure measurement would be to select a low initial pump rate and then increase the pump rate. However, as previously discussed this limits the speed at which the sleeve can be filled. Rather, it is desired to select a pump rate that starts out higher then the desired fill rate but that produces an initial restrictive backpressure measurement that can be reduced so as to have an acceptable error measurement by the time that the desired fill pressure is reached (preferably the gauge pressure and the chamber pressure would be in equilibrium).

For example, referring back to the example above. If the pump 200 was operated at 50 mmHg, the initial restrictive backpressure measurement may be 10 mmHg (as read at the gauge 210). When the sleeve was at: 10 mmHg the gauge 210 may be at 18 mmHg (8 mmHg restrictive backpressure); 20 mmHg the gauge 210 may be at 25 mmHg (5 mmHg restrictive backpressure); 30 mmHg the gauge 210 may be at 31 mmHg (1 mmHg restrictive backpressure); and 40 mmHg the gauge 210 may be at 41 mmHg (1 mmHg restrictive backpressure). In this example, the gauge pressure and the sleeve pressure became in equilibrium at approximately 30 mmHg (31 mmHg at the gauge 210). Accordingly, when the gauge 210 reads 35 mmHg the actual pressure of the sleeve chamber may be 34 mmHg. This would be an accuracy of approximately 97%.

It is possible through various means including calculations and experimentations to determine pump pressure settings to be used for desired fill pressures. The pump values may be defined for each desired fill value or the fill values may be grouped together and the pump setting may be defined for the groups. For example, desired fill pressures in the ranges of 0-30 mmHg, 30-45 mmHg, 45-60 mmHg, 60-75 mmHg, and 75-120 mmHg, may equate to the pump operating at 40 mmHg, 60 mmHg, 75 mmHg, 90 mmHg and 120 mmHg respectively. These pump pressures may produced initial restrictive pressure measurements of 12 mmHg, 16 mmHg, 20 mmHg, 26 mmHg and 32 mmHg respectively.

It is necessary to modify the pump output to generate a pressure that is less then the full pressure of the pump 200. One way to modify the operation of the pump 200 is to provide a variable resistance that limits the power applied to the pump 200 based on the desired output. A higher resistance is applied to decrease the power and corresponding pump output. This embodiment requires the pump 200 to be operational at all times but that the power provided to the pump 200 be throttled.

Another way to modify the operation of the pump 200 is to control the duty cycle of the pump 200. That is, switch the pump 200 off for a portion of the possible on-time so that it is not always operational. Reducing the time that the pump 200 is on during a given interval will reduce the pressure output of the pump 200. The duty cycle of the pump 200 may be defined simply in terms of time (e.g., 3 microseconds) or may be defined in terms of cycles (e.g., clock, power). According to one embodiment, the duty cycle is a relatively small amount of time so that there is an impact on the pressure generated. If the duty cycle is too large it may have the effect of generating a maximum pressure output for a certain amount of time and then generating no pressure output for a certain amount of time.

According to one embodiment, the duty cycle is tied to the power signal (e.g. 60 Hz AC power) operating the pump 200. The portion of the duty cycle that the pump 200 is active (or non-active) may correspond to the ratio of the desired pressure to maximum pressure. For example, in a case where the maximum pump pressure is 100 mmHg and the desired pressure is 70 mmHg (e.g., 70% full capacity or 30% reduction) the pump 200 may be operational for 70% (or non-operational for 30%) of the corresponding duty cycle. The above examples appear to indicate a linear relationship between the capacity of the pump 200 and the on-time of the duty cycle, but it is not limited thereto.

There may be a duty cycle associated with each possible pump pressure output. Alternatively, a certain duty cycle may be associated with a range of pump outputs (e.g., 90-120 mmHg is 100% duty cycle, 60-90 mmHg is 75% duty cycle). If specific pump operating pressures were defined for groups of desired filled pressures as noted above a duty cycle could be associated with each of the defined operating pressures.

Where the AC power frequency is 60 Hz the duty cycle would be 1/60^(th) of a second or approximately 16.7 milliseconds. The pump 200 may then be controlled to be turned on for 70% of the duty cycle (approximately 11.7 milliseconds) and off for 30% of the duty cycle (approximately 5 milliseconds).

FIG. 3 illustrates an example functional diagram of a duty cycle control system 300 utilized in a compression pump system. The duty cycle control system 300 determines and controls the pump 340 on-time. The duty cycle control system 300 may include a timing device 310, a processing device 320, and a power-switching device 330. The timing device 310 may be used to track the duty cycle and signal the processing device 320 each time a duty cycle transition occurs (one duty cycle ends and another begins). If the duty cycle was defined in terms of time (e.g., 10 milliseconds) the timing device 310 may track each 10 millisecond period and signal the processing device 320 at the start of the next one. If the duty cycle corresponds to the input AC power frequency, the timing device 310 may detect the beginning of each new wave and inform the processing device 320 of the new cycle.

If the duty cycle is half the AC power wave the timing device 310 may detect each half wave by detecting when the wave crosses over zero voltage. According to one embodiment, the timing device 310 may be an opto-isolator for detecting the zero voltage crossover and the beginning of each new half cycle. As one skilled in the art would recognize, there are numerous methods by which a duty cycle can be defined and monitored.

The processing device 320 receives an input from the timing device 310 that a duty cycle transition has occurred (duty cycle input). The processing device 320 may use the duty cycle input to either start or stop the pump. According to one embodiment, the processing device 320 may stop the operation of the pump 340 when the duty cycle input is received and delay starting the operation of the pump 340 for a certain portion of the duty cycle based on the desired pressure. For example, the processing device 320 may delay the start of the pump 340 for 30% of the duty cycle (e.g., 3 milliseconds if the duty cycle was 10 milliseconds, 5 milliseconds if the duty cycle was a 60 Hz AC power cycle). At the end of the delay the pump 340 is then turned on and may then remain on until the next duty cycle input is received at which point the pump 340 would be turned off again.

According to another embodiment, the processing device 320 may start the operation of the pump 340 when the duty cycle input is received and maintain the operation of the pump 340 for a certain portion of the duty cycle based on the desired pressure. For example, the processing device 320 may leave the pump 340 on for 70% of the duty cycle (e.g., 7 milliseconds if the duty cycle was 10 milliseconds, 11.7 milliseconds if the duty cycle was a 60 Hz AC power cycle). The pump 340 may then be turned off and remain off until the next duty cycle input is received at which point the pump 340 would be turned on again.

The processing device 320 signals the power-switching device 330 to turn the pump 340 on or off. The power-switching device 330 either provides or removes power to the pump 340 based thereon. In effect, the power-switching device 330 acts as a switch between a power source and the pump 340. According to one embodiment, the switching device 330 is a solid-state relay. When directed to turn the pump 340 on, the switch is closed so that power is provided to the pump 340. When directed to turn the pump 340 off, the switch is open so that the pump 340 does not receive power.

A pressure sensor 350 may measure the pressure associated with each sleeve (at the manifold) and feedbackpressure data to the processing device 320. The processing device 320 can use the pressure data to further control the system. For example, the processing device 320 may direct the manifold to switch chambers once the desired pressure is obtained for a filled chamber. If all the chambers are filled the processing device 320 may turn the pump 340 off, may open some or all of the valves, or activate a vent valve to deflate the filled chambers. The processing device 320 may also utilize the pressure data to further throttle the pump 340 when the measured pressure is close to the desired fill pressure.

The processing device 320 may be programmed with different parameters to control the operation of the pump 340 depending on the desired fill pressure of a sleeve. For example, the processing device 320 main contain look up tables that equate desired fill pressures to operational pump pressure, and equate operational pump pressure to percentage of duty cycle that pump is on (or off). The parameters may be contained in one or more look-up tables. The parameters (e.g., look-up tables) may be stored in memory. The memory may be contained within the processor device 320 or may be in an external memory device that the processor device 320 can read.

The desired pressure for each chamber may be programmed individually or the desired pressure in the first chamber and the gradient (change between chambers) may be defined.

By way of example, assume that we have an eight chamber system and that the pressure of the first chamber is set at 60 mmHg with a 5 mmHg gradient. The initial pump pressure to provide 60 mmHg for the first chamber may be 80 mmHg. The 80 mmHg pump operation may be equated to a duty cycle of 75% and produce a initial restrictive backpressure of 22 mmHg. The initial pump pressure to provide 55 mmHg for the second chamber, 50 mmHg for the third chamber, and 45 mmHg for the fourth chamber may be 70 mmHg. The 70 mmHg pump operation may be equated to a duty cycle of 70% and produce a initial restrictive backpressure of 18 mmHg. The initial pump pressure to provide 40 mmHg for the fifth chamber, 35 mmHg for the sixth chamber, and 30 mmHg for the seventh chamber may be 55 mmHg. The 55 mmHg pump operation may be equated to a duty cycle of 60% and produce a initial restrictive backpressure of 14 mmHg. The initial pump pressure to provide 30 mmHg for the eighth chamber may be 40 mmHg. The 40 mmHg pump operation may be equated to a duty cycle of 50% and produce a initial restrictive backpressure of 12 mmHg.

By operating the pump at a maximum pressure that limits the effect of the restrictive backpressure on the pressure measured at the gauge (maintain a fairly accurate pressure measurement) allows the chambers to be filled in a much quicker and efficient manner than prior art systems without sacrificing accuracy.

If after the system is established the resistive backpressure increases for some reason (e.g., kink in the tubing connecting the valve to the chamber, extra tubing added) the accuracy of the pressure readings may decrease. For example, the increased backpressure may delay the point where the pressure recorded at the gauge and the pressure within the chamber are in equilibrium. This may result in the gauge detecting a desired pressure too soon. One way to reduce the initial resistive backpressure and thus limit the impact to the equilibrium time is to limit the pressure provided from the pump. According to one embodiment, the tubing connecting the pump to the manifold is run through a sleeve that has a set screw in it that can be used to restrict the flow of air and thus reducing the pressure of the air provided to the manifold and the sleeve.

According to one embodiment, the system includes a user interface that easily allows one to change parameters (e.g., number of chambers, desired fill pressure, gradient, therapy time, etc.). Enabling these parameters to be changed may allow doctors to experiment with different therapy options. For example, doctors may study which pressure gradients or fill times are more effective for different maladies.

According to one embodiment, the user interface system may be deactivated so that the parameters programmed in cannot be changed. The deactivation may be a simple switch or may be a programmed system mode under password protection. A physician or medical technician may use this feature to disable the patient's ability to access and modify the program.

According to one embodiment, the system includes a display that illustrates associated system parameters. The parameters may include the amount of time remaining in a therapy session, the chamber being filled, the amount of pressure being applied in each chamber, etc. The parameters may be displayed on an analog meter, a bar graph, or as a number.

According to one embodiment, the compression pump system includes a fully functioning wireless remote control device. This remote unit may operate all keyboard keys and system programming functions. This device also may be enabled or disabled by a switch or program control feature.

According to one embodiment the system is programmed to fill all of the chambers at once rather than sequentially in order to provide an alternate treatment option.

Although the invention has been illustrated by reference to specific embodiments, it will be apparent that various changes and modifications may be made. Reference to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” or “in an embodiment” appearing in various places throughout the specification are not necessarily all referring to the same embodiment.

Different implementations may feature different combinations of hardware, firmware, and/or software. For example, some implementations feature computer program products disposed on computer readable mediums. The programs include instructions for causing processors to perform techniques described above.

It is intended that the various embodiments be protected broadly within the spirit and scope of the appended claims. 

1. An apparatus comprising a compressor pump; a duty cycle controller to control amount of time that said compressor pump is on each duty cycle, wherein the amount of time is selected so that said compressor pump will operate at a pressure above a desired fill pressure that will generate a restrictive pressure having limited effect on accuracy of pressure reading.
 2. The apparatus of claim 1, wherein the pressure reading is measured at a manifold that routes air from said pump to a destination and the desired fill pressure is associated with the destination.
 3. The apparatus of claim 2, wherein the destination is a chamber of a compression sleeve.
 4. The apparatus of claim 3, wherein the restrictive pressure is based on at least some subset of length or tubing connecting the manifold to the chamber, size or valve in manifold, and residual pressure in chamber.
 5. The apparatus of claim 1, wherein the duty cycle is a measure of time.
 6. The apparatus of claim 1, wherein the duty cycle corresponds to an input AC power frequency.
 7. The apparatus of claim 1, wherein the duty cycle corresponds to half of an input AC power frequency wave.
 8. The apparatus of claim 1, wherein said duty cycle controller includes a timing device to detect start of next duty cycle; a processing device to determine and control amount of time that pump is operational per duty cycle; and a power switching device to control power provided to said pump responsive to the processing device.
 9. The apparatus of claim 8, further comprising memory having different parameters stored therein, and wherein said processing device uses the different parameters to determine the amount of time pump is operational per duty cycle.
 10. The apparatus of claim 1, wherein the desired fill pressure is selectable.
 11. A compression pump system comprising a compressor pump; a manifold having at least one valve to route pressurized air; a compression device having at least one chamber, wherein each chamber is associated with a valve; a pressure sensor, located at the manifold, to monitor pressure of the chambers, wherein operation of the valves is responsive to measurements of said pressure sensor; and a controller to operate said compressor pump at an operational pressure above a desired fill pressure and that will generate a restrictive pressure having limited effect on accuracy of pressure reading at said pressure sensor.
 12. The system of claim 11, wherein said controller utilizes variable resistance to select the operational pressure.
 13. The system of claim 11, wherein said controller generates the operational pressure by modifying portion of duty cycle said pump is operational.
 14. The system of claim 13, wherein said controller includes a timing device to detect start of next duty cycle; a processing device to determine and control amount of time that pump is operational per duty cycle; and a power switching device to control power provided to said pump responsive to the processing device.
 15. The system of claim 14, wherein the timing device is an opto-isolator that determines a start of each AC half wave by detecting a zero voltage crossover.
 16. The system of claim 11, further comprising a user interface to enable a user to set desired pressure in the chambers.
 17. The system of claim 11, wherein the user interface enables a user to set an initial chamber pressure and a gradient between each chamber.
 18. A method comprising selecting desired fill pressure; determining compressor pump output pressure; determining appropriate amount of time that a compressor pump is on each duty cycle to generate the pump output pressure.
 19. The method of claim 18, wherein the pump output pressure will operate at a pressure above the desired fill pressure and will generate a restrictive pressure having limited effect on accuracy of pressure reading.
 20. The method of claim 18, further comprising detecting beginning of a duty cycle; and applying power to the compressor pump for the appropriate amount of time during each duty cycle. 